Scale-up synthesis of hyperbranched poly(amidoamine)-grafted ultrafine silica using dendrimer synthesis methodology in solvent-free dry-system

Scale-up synthesis of hyperbranched poly(amidoamine)-grafted ultrafine silica was successfully achieved by using dendrimer synthesis methodology in solvent-free dry-system. The poly(amidoamine) was allowed to grow from silica surface by repeating two steps: (1) Michael addition of methyl acrylate (MA) to amino group on the surface and (2) amidation of terminal ester group with ethylenediamine (EDA). MA was sprayed onto silica having amino group and the silica agitated at 300 rpm at 50degreesC. After the reaction, unreacted MA was removed under vacuum. Then EDA was sprayed and the reaction was conducted at 50degreesC with agitation. After the reaction, unreacted EDA was also removed under vacuum at 50degreesC and MA was sprayed again. The percentage of poly(amidoamine) grafting onto the surface was determined to be 141% with repeated reaction cycles of eight-times. However, the value was considerably smaller than that of the theoretical value. This indicates that the propagation of poly(amidoamine) dendron from silica surface was not achieved theoretically and hyperbranched poly(amidoamine) was grafted onto the surface because of steric hindrance of grafted polymer. In addition, the effect of initial amino group content on the growth of poly(amidoamine) from the surface was investigated. It was concluded that the method is suitable for the scale-up synthesis of hyperbranched poly(amidoamine)-grafted silica. Copyright (C) 2002 John Wiley Sons, Ltd.